The quick-closing and control valves used in steam turbines are usually located outside and separate from the turbine casing and are connected to the latter by pipe bends entering the casing at right angles. The pipe bends are shaped so that they permit elastic deformations to compensate for the thermal expansions without high thermal stresses appearing in the process. In this arrangement, the pipe bends extend far upwardly from the turbine casing with a corresponding space requirement in the hall, so that such large vertical pipe bends involve large hall heights with corresponding additional costs as compared to a lower power station hall. The pipe bends themselves, however, are also expensive and present substantial sealing problems in the region of the flange connections because of the high steam pressures. In order to avoid these problems, control valves in the vertical position have been flanged directly on the upper part of the turbine casing or welded to their casing block. The disadvantage of the large installation height, however, remains.
In order to avoid this disadvantage, control valves are similarly flanged or welded directly in a horizontal position on the upper part of the casing, but exclusively in the case of single casing turbines. Up to now, however, this could only be practised with single casing turbines because only in these turbines can the valve or valves be raised upwards, alone or together with the casing, in the case of inspections.
In the case of double casing turbines, in which only the exhaust steam pressure is present in the intermediate space bounded by an inner casing shell and an outer casing shell, the outer casing being consequently relieved of the high pressure of the working steam, the control valves were either fastened directly to the outer casing in a vertical position and connected flexibly and so as to seal with the inner casing, or the valves were connected to the inner casing via a pipe entering at right angles into the inner casing, which pipe was flanged to the outer casing. This arrangement does not, therefore, permit the raising of the casing upper part during inspections without the supply pipes and the associated fastening devices also having to be removed.
For a relatively long time, therefore, there has been a requirement for a valve design which, while avoiding the supply pipes mentioned between the valve and the turbine casing upper part, can be attached directly to the latter in a horizontal position and makes it possible to raise the turbine casing upper part without further complication after the removal of the valve.